It is known that conjugated dienes can be carbonylated using various palladium catalysts. Depending on the nature of the hydroxyl group-containing compound used as coreactant various alkanedioic derivatives can be obtained. For example, carboxylic acid esters will be obtained in the presence of alcohols, carboxylic acids in the presence of water, and carboxylic anhydrides in the presence of carboxylic acids.
While dienes have two double bonds potentially available for carbonylation, most of the known processes result in the carbonylation of only one of these double bonds and forms monofunctional alkenoic derivatives. For the production of difunctional derivatives, it is required to isolate this alkenoic intermediate product and to subject it to carbonylation of its remaining double bond in a separate step.
Thus, U.S. Pat. No. 4,861,912 discloses a two-step process for the preparation of adipic acid or esters. In U.S. Pat. No. 4,861,912, 1,3-butadiene is carbonylated using a catalyst system containing a palladium compound and a bidentate diphosphine ligand having aromatic substituents on the phosphorus atoms in a first step forming a pentenoic acid or ester, subsequently isolating the pentenoic acid or ester obtained, followed by carbonylating the isolated pentenoic acid or ester in the presence of a second carbonylation catalyst. The requirement of isolation of the intermediate product makes this known process more laborious.
U.S. Pat. No. 4,691,047 discloses a process for the direct conversion of conjugated diene into carboxylic diacids or diesters using a catalyst system containing a palladium compound, an aryl-substituted monophosphine, optionally in conjunction with an aryl-substituted bidentate diphosphine, and at least one mole of hydrogen chloride per atom of trivalent phosphorus present in the catalytic system. Due to the corrosive nature of hydrogen chloride, this known process suffers from severe equipment requirements when being conducted on an industrial scale. Also, the monophosphine component of this catalyst system tends to become inactivated under the conditions applied.
It is therefore an object of the present invention to provide an improved direct process to prepare alkanedioic derivatives by the reaction of an aliphatic conjugated diene with carbon monoxide and a hydroxyl group-containing compound.